This invention concerns glass optical fibers and optical fiber preforms having multiple holes or openings or voids running the entire length, and methods of making.
This disclosure also concerns an extrusion die with multiple joining channels manufactured by an additive manufacturing technique.
Optical fibers can be used to route light from one point to another, with losses that are dependent on the optical fiber design, material used and wavelength transmitted. The optical transmission window of materials is limited by a short wavelength edge, mostly due to electronic transitions, and a long wavelength edge, mostly due to multi-phonon transitions.
For different materials the transmission edges might lie in different ranges of the optical spectrum. The choice of fiber geometry and design affect the degree of overlap between the propagating light and the material.
A solid core fiber such as step index has a large modal overlap with the material, while hollow core photonic band gap fibers can have a small overlap. The impact of the combined limits from material loss and effective light guidance of a given fiber is to limit the range of wavelengths that can effectively be transmitted in the fiber.
The range of wavelengths that can be transmitted by solid core optical fibers are mainly limited by the material transmission. For example, silica based fibers being restricted to transmitting visible and shortwave infrared bands, while selenide-based fibers transmit part of the shortwave infrared band, the mid-infrared band and a part of the long-wave infrared band. Alternative fiber designs, where the light propagates in a hollow air core such as hollow-core photonic crystal fibers relax some of the wavelength transmission restrictions.